Field of the Invention
The disclosed and claimed concept relates to forming a cup-shaped body and, more specifically, to providing an inwardly extending dome to a cup-shaped body.
Background Information
It is known in the container-forming art to form two-piece containers, e.g., cans, in which the walls and bottom of the container are a one-piece cup-shaped body, and the top or end closure is a separate piece. After the container is filled, the two pieces are joined and sealed, thereby completing the container. The cup-shaped body typically has a domed end. That is, the cup-shaped body typically begins as a flat material, typically metal, either in sheet or coil form. Blanks, i.e., disks, are cut from the sheet stock and then drawn into a cup. That is, by moving the disk through a series of dies while disposed over a ram or punch, the disk is shaped into a cup having a bottom and a depending sidewall. The cup may be drawing through additional dies to reach a selected length and wall thickness. One of the last deformations applied to the cup is forming an inwardly extending dome to the bottom of the cup. That is, the cup is moved into engagement with a domer; the domer having a domed end onto which the cup is pressed. This action typically occurs at the end of the stroke of the punch. In this configuration, the presses produce excessive noise, vibration and stress on the press due to the engagement of the ram with the domer.
That is, when the punch, having a cup-shaped body disposed thereon, engages the domer, there is an impact. The impact is noisy, causes the press to vibrate, and induces stress on both the punch and the domer. This is especially true if the domer is fixed. One method of reducing the force of the impact was to provide a floating domer, i.e., the domer was movable in a direction parallel to the longitudinal axis of the punch. In such a device, the domer could be mounted on a spring and/or a piston. In this configuration, after the bottom of the cup-shaped body was deformed, the domer could move away from the punch, thereby reducing the force of the impact. The disadvantage to this configuration is that the domer was still structured to apply the force required to deform the cup-shaped body in, essentially, a single instant. While the movable domer reduced some of the force of the impact, the force was still significant.